The present invention relates to a permanent magnet rotary motor.
Japanese Patent Application Laid-Open Publication No. 199630/2002 (hereinafter referred to as Patent Document 1) discloses a brushless motor including a stator core constituted by fitting a first divided core unit into a second divided core unit. The first divided core unit is shaped to constitute an annular yoke. The second divided core unit is constituted by including a plurality of pole pieces around which exciting wiring portions are wound, a plurality of magnetic surface constituent portions provided at ends of the pole pieces, respectively, and a plurality of connecting portions each coupling two adjacent magnetic surface constituent portions to each other. The pole pieces, magnetic surface constituent portions, and the connecting portions are formed integrally with one another. In a rotor in this conventional brushless motor, the number of permanent magnets is made to be different from the number of the pole pieces. Further, lengths of the connecting portions in a circumferential direction of the annular yoke are made to be different. Reduction in torque pulsation (cogging torque) is thereby achieved.
Japanese Patent Application Laid-Open Publication No. 10539/2002 (hereinafter referred to as Patent Document 2) discloses an armature of a motor including a stator core in which two adjacent magnetic pole surface constituent portions are connected by a connecting portion, thereby closing a slot. In this stator core, a plurality of openings are formed in connecting portions for closing the slots. The openings are formed in an axial line direction of a rotary axis of the motor in a discontinuous manner and open in a radially inward direction and toward slots. These openings are provided to prevent magnetic flux leakage between magnetic poles.
In the motor disclosed in Patent Document 1,however, sectional shapes of respective slots of the motor are different. Accordingly, the lamination factor of windings among a slot cannot be made to be constant. Then, when the number of the windings is therefore increased to increase the torque, the size of the stator core will be increased.
The motor disclosed in Patent Document 2 further needs a step of forming the openings in the connecting portions that pass through in the radial direction of a rotor after steel plates have been rotated and laminated. The number of manufacturing steps is therefore increased. In addition, manufacture of the motor is very complicated.
An object of the present invention is therefore to provide a permanent magnet rotary motor in which cogging torque can be reduced without greatly reducing torque and in which the lamination factor of windings within each slot can be enhanced.
Other object of the present invention is to provide a permanent magnet rotary motor that can be easily manufactured and can also reduce the cogging torque.